Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Common stock, beginning balance (in shares) at Jul. 31, 2018		38,860,571
Beginning balance at Jul. 31, 2018	$ 505,684,000	$ 3,886,000	$ 538,453,000	$ 405,194,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Jul. 31, 2018					15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	2,237,000		2,237,000
Proceeds from exercises of stock options (in shares)		6,100
Proceeds from exercises of stock options	174,000	$ 1,000	173,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		20,198
Proceeds from issuance of employee stock purchase plan shares	476,000	$ 2,000	474,000
Issuance of restricted stock (in shares)		10,386
Forfeiture of restricted stock	$ 0	$ 1,000	(1,000)
Net settlement of stock-based awards (in shares)	9,345	53,292
Net settlement of stock-based awards	$ (2,058,000)	$ 5,000	(2,063,000)
Cash dividends declared	(4,764,000)			(4,764,000)
Accrual of dividend equivalents, net of reversal	(166,000)			(166,000)
Net income	11,294,000			11,294,000
Common stock, ending balance (in shares) at Jan. 31, 2019		38,950,547
Ending balance at Jan. 31, 2019	512,877,000	$ 3,895,000	539,273,000	411,558,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Jan. 31, 2019					15,033,317
Common stock, beginning balance (in shares) at Oct. 31, 2018		38,938,844
Beginning balance at Oct. 31, 2018	506,096,000	$ 3,894,000	537,852,000	406,199,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Oct. 31, 2018					15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	1,191,000		1,191,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		11,337
Proceeds from issuance of employee stock purchase plan shares	235,000	$ 1,000	234,000
Net settlement of stock-based awards (in shares)		366
Net settlement of stock-based awards	(4,000)		(4,000)
Cash dividends declared	(2,383,000)			(2,383,000)
Accrual of dividend equivalents, net of reversal	(84,000)			(84,000)
Net income	7,826,000			7,826,000
Common stock, ending balance (in shares) at Jan. 31, 2019		38,950,547
Ending balance at Jan. 31, 2019	$ 512,877,000	$ 3,895,000	539,273,000	411,558,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Jan. 31, 2019					15,033,317
Common stock, beginning balance (in shares) at Jul. 31, 2019	39,276,161	39,276,161
Beginning balance at Jul. 31, 2019	$ 535,082,000	$ 3,928,000	552,670,000	420,333,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Jul. 31, 2019	15,033,317				15,033,317
Common stock, ending balance (in shares) at Oct. 31, 2019		39,402,226
Ending balance at Oct. 31, 2019	$ 537,644,000	$ 3,940,000	551,316,000	424,237,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Oct. 31, 2019					15,033,317
Common stock, beginning balance (in shares) at Jul. 31, 2019	39,276,161	39,276,161
Beginning balance at Jul. 31, 2019	$ 535,082,000	$ 3,928,000	552,670,000	420,333,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Jul. 31, 2019	15,033,317				15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	$ 2,117,000		2,117,000
Proceeds from exercises of stock options (in shares)		16,700
Proceeds from exercises of stock options	468,000	$ 2,000	466,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		20,010
Proceeds from issuance of employee stock purchase plan shares	510,000	$ 2,000	508,000
Issuance of restricted stock (in shares)		8,858
Forfeiture of restricted stock	$ 0	$ 1,000	(1,000)
Net settlement of stock-based awards (in shares)	27,902	107,326
Net settlement of stock-based awards	$ (3,459,000)	$ 10,000	(3,469,000)
Common stock issued for acquisition of CGC Technology (CGC) (in shares)		323,504
Common stock issued for acquisition of CGC Technology (CGC)	11,575,000	$ 32,000	11,543,000
Cash dividends declared	(4,860,000)			(4,860,000)
Accrual of dividend equivalents, net of reversal	(113,000)			(113,000)
Net income	$ 9,883,000			9,883,000
Common stock, ending balance (in shares) at Jan. 31, 2020	39,752,559	39,752,559
Ending balance at Jan. 31, 2020	$ 551,203,000	$ 3,975,000	563,834,000	425,243,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Jan. 31, 2020	15,033,317				15,033,317
Common stock, beginning balance (in shares) at Oct. 31, 2019		39,402,226
Beginning balance at Oct. 31, 2019	$ 537,644,000	$ 3,940,000	551,316,000	424,237,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Oct. 31, 2019					15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	1,238,000		1,238,000
Proceeds from exercises of stock options (in shares)		6,100
Proceeds from exercises of stock options	162,000	$ 1,000	161,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		9,875
Proceeds from issuance of employee stock purchase plan shares	264,000	$ 1,000	263,000
Forfeiture of restricted stock (in shares)		(12,652)
Forfeiture of restricted stock	0	$ (1,000)	1,000
Net settlement of stock-based awards (in shares)		23,506
Net settlement of stock-based awards	(686,000)	$ 2,000	(688,000)
Common stock issued for acquisition of CGC Technology (CGC) (in shares)		323,504
Common stock issued for acquisition of CGC Technology (CGC)	11,575,000	$ 32,000	11,543,000
Cash dividends declared	(2,432,000)			(2,432,000)
Accrual of dividend equivalents, net of reversal	(57,000)			(57,000)
Net income	$ 3,495,000			3,495,000
Common stock, ending balance (in shares) at Jan. 31, 2020	39,752,559	39,752,559
Ending balance at Jan. 31, 2020	$ 551,203,000	$ 3,975,000	$ 563,834,000	$ 425,243,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Jan. 31, 2020	15,033,317				15,033,317